CCIC(Climate Change Information Center)


KGAWC(Korea Global Atmosphere Watch Center)

   KMA(Korea Meteorological Administration) operates World Calibration Centre for Sulphur Hexafluorid (WCC-SF6), one of the central facilities in the World Meteorological Organization / Global Atmosphere Watch(WMO/GAW) programme, from October 2012. The duties of WCC-SF6 are follows;

a) assist WMO members operating WMO/GAW stations to link their sulphur hexafluoride (SF6) observations to the WMO/GAW
Reference Scale through comparisons with standards calibrated against the primary/secondary standards maintained
by the Central Calibration Laboratory for SF6;

b) assist the WMO/GAW Scientific Advisory Group (SAG) on Greenhouse Gases in the development of the quality control
procedures required to support the quality assurance of SF6 measurements and ensure the traceability of these
measurements to the corresponding primary standard;

c) maintain laboratory and transfer SF6 gas standards that are traceable to their respective primary standard(s);

d) perform regular calibrations and inter-comparison campaigns involving the WMO/GAW stations/laboratories;

e) assist in provision of training and long-term technical help for WMO/GAW stations; and

f) make public its involvement in the WMO/GAW Programme (e.g. on its websites, in its newsletters).

   WCC-SF6 established several systems for sampling compressed dry air and analyzing SF6 to prepare laboratory and transfer gas standards traceable to the WMO/GAW SF6 Reference Scale. Before preparation of SF6 standard gases, 10 L aluminum cylinders cleaned up with evacuation system with a turbo molecular pump and a heating apparatus more than 12 hours that is able to maintain the residual pressure inside the cylinder less than 0.1 Pa. (Fig. 1(a)) Dry air sample was collected by an oil free air compressor connected through Dekabon tube from the top of 40 m height sampling tower. (Fig. 1(b) and (c)) To remove moisture in air sample, a chemical trap filled with granulated magnesium perchlorate was used. (Fig. 1(d)) After preparation of compressed air in the cylinder, a SF6 mole fraction of the sample assigned by a gas chromatograph with electron capture detector (GC/ECD) and five standard gases with the WMO SF6 mole fraction scale maintained by the CCL (NOAA). (Figs. 2, 3)

Cylinder evacuation system Sampling tower(40m) Air compressor room Air sampling system
(a) Cylinder evacuation system (b) Sampling tower
(40 m height)
(c) Air compressor room (d) Air sampling system

Figure 1. Systems for preparation of compressed dry air in the cylinder

Pre-concentrator SF6 analyzer(GC-ECD) SF6 standards(WMO mole fraction scale)
(a) Pre-concentrator (b) Analytical system (c) NOAA X2014 scale

Figure 2. Analytical system and WMO reference scale (NOAA X2014) to prepare for labotory and transfer standards gases, which are traceable to the WMO reference scale

Calibration curve Chromatogram

Figure 3. Calibration curve (left) and chromatogram (right) of the five NOAA SF6 standard gases